JPS61129454A - Air fuel ratio controller for internal-combustion engine - Google Patents

Abstract

PURPOSE:To suppress the variation of air fuel ratio during operation by controlling the opening degree of a purge control valve, according to the signals supplied from an air fuel ratio sensor, in a canister installed at the edge of a purge passage opened into a suction pipe. CONSTITUTION:One side of a canister 40 filled with the absorbent 40a such as active carbon is opened to the atmosphere through an atmosphere introducing pipe 42, and the other side is connected to the upper space of a fuel tank 46 through an evaporated fuel pipe 44, and connected to a surge tank 26 in a suction system through a purge pipe 48. In this case, a purge control valve 50 having a butterfly-type valve piece 52 is installed into the purge pipe 48, and is drive-controlled by a revolution drive type actuator 56. Said actuator 56 is controlled according to the output of an air fuel ratio sensor 70 installed onto an exhaust manifold 32 by a control circuit 60, and always proper purge control is performed, and the variation of air fuel ratio is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a control device for a so-so flow rate in an internal combustion engine with a canister thrown.

BACKGROUND OF THE INVENTION In internal combustion engines for automobiles, a canister is provided to collect fuel vapor from a fuel tank or a float chamber of a carburetor. An adsorbent layer such as activated carbon is formed inside the canister, and evaporated fuel from the engine is temporarily adsorbed on the adsorbent layer. The adsorbed fuel is removed by a purge air flow caused by the negative pressure in the intake pipe and reintroduced into the engine.

Problems to be Solved by the Invention The purge air flow for removing the fuel adsorbed in the canister is generated by the pressure difference between the intake pipe negative pressure and the atmospheric pressure. The smaller the throttle valve opening, the stronger the negative pressure in the intake pipe. As a result, a large amount of fuel is removed during idling or deceleration, resulting in the problem that the air-fuel ratio becomes excessively rich or fluctuates during idling or deceleration. Therefore, techniques have been proposed to limit or stop the noise during idling or deceleration. However, this measure is not sufficient as a countermeasure against fluctuations in air-fuel ratio (
).

Therefore, it has been proposed that an air-fuel ratio sensor is provided and purge control is performed based on the air-fuel ratio signal from the sensor. For example, see Japanese Patent Publication No. 57-129247. This conventional technology uses signals from an oxygen concentration battery-type air-fuel ratio sensor installed in the exhaust pipe, such as a
The purge control valve provided in the merge passage is opened and closed, thereby controlling the air-fuel ratio to a predetermined value of 5. However, since the 02 sensor can only perform ON-OFF control, it is not a decisive factor in eliminating air-fuel ratio fluctuations.

Means for Solving the Problems In the internal combustion engine of the present invention, as shown in FIG. 1, a canister C is installed at the end of a purge passage P that opens into the intake pipe of the internal combustion engine E. The air-fuel ratio control device includes a purge control valve V with a continuously variable flow rate installed on the purge passage P;
・A drive actuator A for the purge control valve, an air-fuel ratio detection means 1 that detects the continuously changing air-fuel ratio, and an i4- that calculates the purge flow rate according to the air-fuel ratio signal from the air-fuel ratio detection means 1. The control means 3 comprises a flow rate calculation means 2 and a control means 3 for driving the actuator A so as to obtain the calculated flow rate.

Operation) The 4-quantity calculation means 2 calculates the purge flow rate according to the continuously changing air-fuel ratio detected by the air-fuel ratio detection means 1. The control means 3 controls the actuator A so as to obtain the calculated purge flow rate, and the control valve V controls the purge amount flowing through the merge passage P so that the air-fuel ratio becomes a predetermined value.

Embodiment In FIG. 2, 10 is a cylinder block, 12 is a piston, 14 is a cylinder head, 16 is a combustion chamber, 18 is an intake valve, 19 is an intake port, 20 is an exhaust valve, and 22 is an exhaust port. The intake port 19 is sequentially connected to a fuel injection valve 23, an intake pipe 24, a surge tank 26, a throttle valve 28, an air flow meter 30, and an air cleaner 32.

On the other hand, the exhaust port 22 is connected to the exhaust manifold 32 and the exhaust pipe 3.
4. Catalyst converters 36iC are sequentially connected.

38 is a distributor.

40 is a canister, which houses an adsorbent such as activated carbon 40a in a case. At -m, the canister is opened to the atmosphere by an air introduction pipe f42, and one end of an evaporative fuel pipe 44 is connected to the other side, and the other end communicates with the space above the fuel level of the fuel tank 46. One end of the pump 48 is connected to the side of the canister 40 where the evaporated fuel pipe 44 is installed, and the other end is communicated with the portion 1 of the intake pipe downstream of the throttle valve 28, such as the surge tank 26. A one-way control valve 50 is disposed above the nozzle arm f4B, and is capable of continuously variable control of the purge flow rate. As shown in Figure 3.4, 5K, A'
- The control valve 50 is constructed by disposing a butterfly-type valve body 52 in a cylindrical case 51 so as to be rotatable by a valve shaft 53. A rotationally driven actuator 56 is attached to one end of the valve shaft 53.
are concatenated.

A continuous rotation type motor such as a servo motor may be used as the actuator, or a step type motor may be used as the actuator. In any case, the opening degree of the valve body 52 is continuously controlled by a drive signal applied to the actuator from a control circuit to be described later, and the purge flow rate is continuously variable controlled.

In FIG. 2, the control circuit 60 is for forming a drive signal for the actuator 56 of the fuel injection valve 23 and the purge control valve 50 so that an air-fuel ratio according to the operating conditions can be obtained, and in the embodiment, the control circuit 60 is a microcomputer system. Constructed as. The control circuit 60 includes a microgrossing unit (MPU) 61, a memory 62, an input port 3, an output port 4, and a path 65 that interconnects these and transfers instructions and data. It consists of M.P.
U61 performs calculations based on signals from various sensors according to a program stored in memory 62, and forms drive signals for fuel injection valve 23 and purge control valve 50. Therefore, signals from various sensors are input to the input 4-) 63. A signal corresponding to the intake air fQ is input from the air flow meter 30. Disl-IJ
A crank angle sensor 68, which is a Hall element facing the magnet piece 38'' on the distribution shaft 38' of the computer 38, generates a pulse signal every predetermined rotation of the engine crankshaft, and the engine N
You can know e. Furthermore, an air-fuel ratio sensor 70 is installed in the exhaust manifold 32 and generates an air-fuel ratio signal Ox.

The air-fuel ratio sensor 70 is not the usual type called 02 Senna, but is a so-called lean sensor based on the principle of oxygen diffusion, or an improved version thereof, and is a type that can measure the air-fuel ratio continuously instead of ON-OFF air-fuel ratio measurement. It is. The basic configuration is shown in FIG. 5, in which an oxygen diffusion layer 72 is installed in a housing 71 so as to form an exhaust gas chamber 73 on one side and an atmospheric chamber 74 on the other side, and a diffusion layer 720 is placed on the opposite side. A pair of electrodes 76 &, b are formed on the electrodes 76 &b, and connected to the DC power source 74 so that the positive side becomes positive on the atmospheric chamber 74 side. In addition to the above basic lean sensor configuration, a pair of electrodes 77a,
In the case of the present invention, it is preferable to use an improved type in which the pump cell 78 is connected to a DC power source 78, which is called an 02 pump cell. Oxygen ions diffuse into the oxygen diffusion layer 72 in an amount corresponding to the oxygen concentration in the exhaust gas, that is, the air-fuel ratio. Therefore, the air-fuel ratio cannot be measured using this principle in the rich region of the 0 air-fuel ratio where a current according to the oxygen concentration is generated in the electromotive force detector 79, but the ion flow generated in the opposite direction by the 0□ pump cell 8 causes the air-fuel ratio to be measured in the rich region. However, the oxygen diffusion layer is modified to be relatively lean, and an electromotive force is generated even in the rich region, and the overall characteristics are as shown in 510 in Figure 6.
This enables continuous measurement of air-fuel ratios over a wide range from rich to lean. This improved sensor is described, for example, in Japanese Patent Application No. 135525/1982.

The present invention may be a normal lean sensor, and the characteristics in this case are as follows.

In FIG. 2, a memory 62 of a control circuit 60 stores a program for air-fuel ratio control according to the present invention. The contents of the program will be explained below using a flowchart. FIG. 7 shows the air-fuel ratio correction routine,
This routine is a time interrupt routine that is executed at predetermined time intervals.

In step 100, calculation of the air-fuel ratio setting value A/F according to the operating conditions is executed. That is, the main 62 has a set air-fuel ratio set (FIG. 10) for each combination of engine speed and intake air amount.

The MPU 61 uses the N signal from the crank angle sensor 68 and the Q signal from the air meter 30 to interpolate the set air-fuel ratio A/F at the time of operation (Fig. 10 p).
.

In step 102, f, the actually measured air-fuel ratio A/FR obtained from the Ox signal from the air-fuel ratio sensor 70 is loaded. 10
In step 4, this measured air-fuel ratio is compared with the set air-fuel ratio A/F at 100, and if the set value deviates in a direction larger than 5%, it is determined that correction should be made in the lean direction, and the process proceeds to step 106. Pipe correction-7iIPFAF described later is δp7i?
Then, in 10B, the feedback correction amount FAF of the fuel injection amount is decremented by δf. If the set value deviates in the direction smaller than 15 inches at 104, it is determined that correction in the rich direction is necessary, and the process proceeds to 110, where the correction PFAF for the armpit amount is incremented by δp.
At step 112, the fuel injection amount correction FAF is incremented by δf. At step 104, when the deviation of the measured air-fuel ratio from the set air-fuel ratio A/F is between 15% and +5, it is determined that there is no need for correction, and at step 114.116, purge correction PPAF and fuel injection amount correction FAF are performed. Let's put together that t.

FIG. 8 shows a fuel injection routine, which is an interrupt routine that enters execution at a fuel injection timing, for example, at a predetermined crank angle. At 200, calculation of the basic fuel injection amount Tp according to the operating conditions is executed. That is, from the air-fuel ratio setting map shown in FIG. 10, a fuel injection amount Tp for obtaining an air-fuel ratio corresponding to the operating conditions is calculated from the rotational speed signal Ne and the intake air amount signal Q. At 202, various well-known fuel injection amount corrections (for example, acceleration correction and temperature correction) α and β are calculated.

204, basic fuel injection amount Tp, feedback correction F
AF (FIG. 7) and calculation of the fuel injection amount T incorporating other corrections α and β are executed. At 206, this value T is set in the output port 4.

Therefore, the fuel injection valve 23 performs fuel injection so that this calculated amount of fuel is injected.

FIG. 9 shows a driving routine for the purge control valve 50, which is a time interrupt routine that is executed at predetermined time intervals.

At 300, calculation of the purge control valve 500 set opening degree (basic opening degree) PUo according to the operating conditions is executed. That is,
The set opening degree of the purge control valve for the combination of engine speed and intake air amount is as shown in FIG. 11. The settings are such that at low loads and low rotations, there is little turbulence, and as the load and rotation increases, the amount of squeezing increases. MPU 6
1 calculates the set opening PU0 of the purge control valve at the time of operation using the rotation speed N@flaw signal e from the rotation speed sensor 6B and the intake air amount signal Q from the air flow meter 30 by an interpolation method (No. 11 r in the figure).

At 302, this calculated basic opening degree PUoIc was obtained by executing the routine shown in FIG.
10, 114) The sum of the armature amount correction PFAF is set as the opening degree PU of the purge control valve.

In step 304, this PUi output is set to It'-)64. Therefore, the actuator 56
The valve body 52 of No. 6 rotates until it reaches the calculated opening, and as a result, the purge amount is such that the set air-fuel ratio is obtained.

Effects of the Invention According to the present invention, more accurate t! - control is realized, air-fuel ratio fluctuations during operation are suppressed, and the amount of harmful components in exhaust gas can be suppressed.

In the past, it was necessary to suppress the air-fuel ratio fluctuations, especially during idling and deceleration, so the noise had to be suppressed, but with the invention of , it is possible to maintain a constant air-fuel ratio, so it is possible to maintain a constant amount of air-fuel ratio during idling and deceleration. 1? - Be able to do the following.

Further, as an effect of the embodiment, as shown in FIG. 11, the amount of purge can be performed in accordance with the operating conditions of the engine, that is, the rotation speed and load. That is, in order to efficiently perform the suction and desorption of the canister, it is necessary to control the purge so that it increases as the load increases. - Load proportional type Tsukuji characteristics can be easily realized by performing feedback control so that the amount of Tsukuji is obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of the present invention. FIG. 2 is a diagram showing an embodiment of the invention. FIG. 3 is an axial sectional view of the purge control valve. FIG. 4 is a cross-sectional view of the NOYA-ZO control valve. FIG. 5 is a diagram showing the principle of an improved sensor that detects a continuously changing air-fuel ratio. FIG. 6 is a graph showing the air-fuel ratio detection characteristics of the sensor shown in FIG. 5. 7 to 9 are flowcharts showing the software configuration of the present invention. FIG. 10 is a diagram showing air-fuel ratio setting values with respect to rotational speed and intake air amount. FIG. 11 is a diagram showing the set value of the opening degree of the control valve No.9-No with respect to the rotational speed and intake air amount. 30... Air 70-meter, 40... Canister,
48... Purge passage, 50... Purge control valve, 60
...Control circuit, 70...Air-fuel ratio sensor. Fig. 1 C... Canister P... Burn passage ■ Purge control valve A, actuator, intake pipe E... Engine Fig. 3 Fig. 4 Fig. 50 Verge control valve Fig. 5 Fig. 6 A/F - "'-' Figure 7 Figure 8 Figure 9

Claims (1)

[Claims] In an internal combustion engine in which a canister is installed at the end of a purge passage that opens into the intake pipe, a purge control valve with a continuously variable flow rate installed on the purge passage, a drive actuator for the purge control valve, and a continuously variable air air-fuel ratio detection means for detecting a fuel ratio; purge flow rate calculation means for calculating a purge flow rate according to an air-fuel ratio signal from the air-fuel ratio detection means; and control for driving the actuator so as to obtain the calculated purge flow rate. An air-fuel ratio control device comprising means.